With the spread of computer systems, mainly personal computers, there has been used a device for inputting new information or giving various instructions to a computer system by pointing at a position on a display screen of a display apparatus on which information is displayed by the computer system, with an indicating object such as a person's finger or a specific tool. In order to perform an input operation with respect to the information displayed on the display screen of the display apparatus of a personal computer or the like by a touching method, it is necessary to detect a touched position (indicated position) on the display screen with high accuracy.
As one example of a device for detecting such an indicated position on the display screen that functions as a coordinate surface, Japanese Patent Application Publication No. 62-32491(1987) discloses an optical position detecting device. This device comprises: an indicating member for pointing at a position on a display screen; at least two optical scanners for emitting scanning light across the display screen; reflecting means for reflecting the scanning light; and means for detecting a time at which the scanning light struck the indicating member, and detects the position of the indicating member on the display screen, based on the relation between the optical scanning start time or end time of the optical scanners and the time at which the scanning light struck the indicating member.
Besides, another optical position detecting device is disclosed in Japanese Patent Application Laid-Open No. 57-211637(1982). This device angularly scans converged light such as a laser beam from the outside of the display screen, calculates angles of a position where a special pen including reflecting means is present from two timings of reflected light from the special pen respectively, and detects the coordinates of the position from the calculated angles using the triangulation principle.
Further, still another optical position detecting device is proposed in Japanese Patent Application Laid-Open No. 62-5428(1987). In this device, light retro-reflectors are positioned as reflecting means on both side frames of the display screen, return light of an angularly scanned laser beam from the light retro-reflectors is detected, an angle of a position where a finger or a pen is present is calculated from a timing that the light beam is blocked by the finger or the pen, and the coordinates of the position is detected from the calculated angles using the triangulation principle.
In an optical position detecting device, when the reflecting means for the scanning light is dirty or when the reflecting means has dust thereon, a proper detecting operation is not performed. However, none of the conventional optical position detecting devices as described above has the function to detect such dirt and dust, and thus there is a problem that operational defects due to such dirt and dust easily occur.
Further, the conventional optical position detecting device including the light retro-reflector detects only a position within the display screen, and thus has a problem that a region between the display screen and the light retro-reflector can not be used effectively.
The present invention has been made with the aim of solving the above problems, and it is an object of the present invention to provide an optical position detecting device capable of using the region outside the display screen effectively, and a recording medium on which the operational program for the same is recorded.
Another object of the present invention is to provide an optical position detecting device capable of detecting dirt on a light retro-reflector and/or dust on or around the light retro-reflector, and a recording medium on which the operational program for the same is recorded.
Still another object of the present invention is to provide an optical position detecting device capable of detecting dirt on a light retro-reflector and/or dust on or around the light retro-reflector and thereby preventing an operational defect caused by such dirt and/or dust, and a recording medium on which the operational program for the same is recorded.
Yet another object of the present invention is to provide an optical position detecting device capable of readily detecting an operational defect of an optical scanning unit (polygon mirror) and thereby enabling a stable operation of the position detection process.
A further object of the present invention is to provide an optical position detecting device capable of detecting dirt on a cover, covering an optical transceiver.